Industry has criticized the study and disputed the researchers claim that St John's wort is one of the most common treatments for ADHD among children.
It has also been criticized for subjecting St John's wort to inappropriate, pharmaceutical-style testing when the herb also known as Hypericum perforatum does not function as a drug.
"Why wasn't a gold standard [double blind, placebo-controlled] used to do a proper comparison?" Daniel Fabricant, PhD, vice president of scientific and regulatory affairs at the Natural Products Association (NPA) told NutraIngredients-USA.com.
"If they're going to set up a drug trial then they should go all out with it. We all know St. John's wort isn't a drug, and traditionally isn't used or intended to be used as a drug."
St John's wort's most commonly studied benefit is in the relief of mild-to-moderate depression and anxiety.
"It's commonly used and has shown efficacy for mild-to-moderate depression in more appropriately designed trials," Fabricant said. "But if you are going to treat it like a drug in a trial, then all the bells and whistles have to be there to accurately tell the whole story. In this instance if the gold standard intervention showed the same lack of effect, would it have been reported that the gold standard didn't work for ADHD?"
He added: "It certainly would have nailed home the lack of quality in this study and made it significantly more difficult to publish and call it peer-reviewed academic medical science."
Usage and quality
The Mayland-based American Herbal Products Association (AHPA) questioned the quality of the St John's wort used in the trial and disputed the researcher's assertion that St John's wort is commonly used to treat ADHD among young people.
"I don't believe that this test material would pass muster if the proposal was submitted to NIH's National Center for Complementary and Alternative Medicine (NCCAM) today because something as basic as ensuring the quality through the duration of the trial was not assured," said Steven Dentali, PhD, AHPA's chief scienceofficer and past chairperson of NCCAM's Product Quality Working Group.
AHPA president, Michael McGuffin, said he knew of no manufacturers marketing St John's wort at children.
"It's an out-of-the-ordinary, rare use. It might be a use that some mom thinks makes sense," he said.
The randomized and placebo-controlled trial was published on June 11 in the Journal of the American Medical Association and involved 54 children ages 6 to 17 years.
Half were given St John's wort, while the other half were given a placebo and no significant difference was found between the two groups in improving the symptoms of ADHD.